What is the difference between timer and watchdog timer?
But, we can explain you the 'watchdog timer'. It is a timing device such that it is set for a preset time interval and an event must occur during that interval. On failure to get that event in the watched time interval, the device generates the timeout signal.
The easiest example to understand the application of a watchdog timer is the mobile phone display.
i.e. the display of your mobile phone is turned off if no GUI interaction happens within a specified time. For eg: You can set it to 10 sec or 20 sec. If you don't touch the screen or use any buttons in that time interval, the display will be off.
This is used to save power.
Want to add little more about watchdog if you're using it in microcontroller then a simple timer gives you a interrupt or any signal when it overflows if your code is hang at any position you can say to program counter. Then also you're recieving interrupt from timer while using watchdog once you'd feed watchdog with predefined time, before that time get's over your program counter must increased or changed if your program counter is remain at same position for that much interval watchdog issues a signal you can use it to take some septicular action like in mobile device to turn off display in case of microcontroller based small application mostly people use it to reset the system. Hope this is clear to you.
Watchdog is a kind of dog which keeps an eye on the software and performs some function whenever the system hangs. This function is normally reset function.
This term watchdog is actually derived from watchman and his dog(watch dog). The responsibility of the watchman and his dog is to protect the society from any kind of illegal activity and if there is any illegal activity, he turns on the alarm.
A timer is a specialized type of clock used for measuring specific time intervals. Timers can be categorized into two main types. A timer which counts upwards from zero for measuring elapsed time is often called a stopwatch, while a device which counts down from a specified time interval is more usually called a timer